dbx mini-pre tube mic preamp is noisy
Ted Roy
it with a Shure SM-7 studio microphone just to find out that this pre-amp is
noisy! I estimated the noise floor to be -50dB with both in/out gain set at
75%. I unplugged the mic, just to hear if the mic/cable causes the noise:
The noise was still present even without the mic/cable plugged at the input.
The only way to make the noise dissapear is either lower the gain or shut
down the unit.
I noticed that the dbx mini-pre is using a Soviet made 12AX7 high-mu twin
triode vacuum tube.
Should I replace this tube with a Genalex 12AX7 ($115) a Mullard 12AX7 ($60)
or with a Telefuken 12AX7 tube? Will the noise go away? Or it's simply the
dbx mini-pre circuit that is noisy and not the soviet tube. I don't want to
invest $115 in a premium quality "replacement" tube, just to find out that I
just got 1 dB improvement in sound....
Thanks for any info.
Info on the dbx mini-pre:
http://www.dbxpro.com/minipre.htm
and
http://www.dbxpro.com/pdf/miniprecut.pdf
Gregg
--
Gregg
On Tue, 28 May 2002 22:14:19 -0400, "Ted Roy" <ted...@hotmail.edu>
wrote:
AT
especially with soft sources.
try it with another mic with a higher output and see what happens.
@
Ted Roy <ted...@hotmail.edu> wrote in message
news:lQWI8.7309$zn5.2...@wagner.videotron.net...
Fred Nachbaur
Ted Roy wrote:
> I just purchased a brand new dbx mini-pre vacuum tube preamplifier. I tested
> it with a Shure SM-7 studio microphone just to find out that this pre-amp is
> noisy! I estimated the noise floor to be -50dB with both in/out gain set at
> 75%. I unplugged the mic, just to hear if the mic/cable causes the noise:
> The noise was still present even without the mic/cable plugged at the input.
>
> The only way to make the noise dissapear is either lower the gain or shut
> down the unit.
>
> I noticed that the dbx mini-pre is using a Soviet made 12AX7 high-mu twin
> triode vacuum tube.
>
> Should I replace this tube with a Genalex 12AX7 ($115) a Mullard 12AX7 ($60)
> or with a Telefuken 12AX7 tube? Will the noise go away? Or it's simply the
> dbx mini-pre circuit that is noisy and not the soviet tube. I don't want to
> invest $115 in a premium quality "replacement" tube, just to find out that I
> just got 1 dB improvement in sound....
>
> Thanks for any info.
If the noise is "hiss", it's unlikely that changing tubes will reduce
this; chances that most of what you're hearing is thermal noise.
However, if it's mechanical noise that's being picked up by the tube
(which you can easily gauge by gently tapping it) then trying different
tubes might help.
HTH,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Freebies, Vacuum Tubes & other stuff: |
| http://www.fna.muohio.edu/dogstar/ |
+--------------------------------------------+
Gregg
SM7, DM57, whichever he uses, the S/N should be at least 90+ dB.
I have measured 12AX7A's at -110dB.
--
Gregg
On Tue, 28 May 2002 22:40:21 -0700, "AT" <spam...@bellsouth.net>
wrote:
jasnider
other tube circut i've ever come across. The tube mod will improve the
sound however. I have heard several people say that this is a worth while
mod to get a decent pre.
J
in article 3cf43e9a...@news.telus.net, Gregg at nos...@unknown.com
wrote on 5/28/02 10:30 PM:
Lynn Fuston
ted...@hotmail.edu wrote on 5/28/02 9:14 PM:
> Should I replace this tube with a Genalex 12AX7 ($115)
Isn't that more than the preamp itself costs?
;-)
Lynn Fuston
3D Audio Inc
Home of the 3dB Recording Forum
http://www.3daudioinc.com/cgi-bin/ultimatebb.cgi
Tim
> down the unit.
Noise from the tubes. No problem, it's natural.
> I noticed that the dbx mini-pre is using a Soviet made 12AX7 high-mu twin
> triode vacuum tube.
Probably good.
> Should I replace this tube with a Genalex 12AX7 ($115) a Mullard 12AX7 ($60)
> or with a Telefuken 12AX7 tube? Will the noise go away?
No. Get a 7025. It's a special 12AX7 that's low noise.
Hay, waddaminit...uuuuuuuuuuuhhhhhhhhhhhhhhmmmmmmmmmmmmmmmmmmmmmmmmm $115....
for a 12AX7.....you....aren't being....serious, are you....nahh, couldn't be...
> Or it's simply the dbx mini-pre circuit that is noisy and not the soviet tube.
If the resistors are carbon comp, you might replace them with carbon or
metal film. Are the resistors right cylinders, curvey shaped, or..?
Tim
--
"WOOHOO! Who would've guessed reading and writing would pay off!"
- Homer Simpson
Jay Ts
>I just purchased a brand new dbx mini-pre vacuum tube preamplifier. I tested
>it with a Shure SM-7 studio microphone just to find out that this pre-amp is
>noisy!
The dbx mini-pre is not a true tube preamp; it uses solid state amplification
along with a starved-plate tube. As far as the noisiness goes, it might suffer
from this low-fi approach that is commonly used in cheap "tube" preamps.
(I tried a Presonus Blue Tube, which is also a starved plate design,
and found it to be unforgivably noisy.)
Try some other microphones and compare. You may just have a low-sensitivity
mic, requiring a lot of gain from the preamp. Often, S/N and dynamic
range specs on equipment are given for operating it with the gain turned
all the way down (with may be a gain of just 1 or 2). When you turn the
gain up (which is what one would usually do with a preamp...) the noise
floor will go up too, possibly to objectionable levels. Caveat emptor.
>The only way to make the noise dissapear is either lower the gain or shut
>down the unit.
No, there is another way to make the noise disappear: put it back in
its box and return it to the dealer for a refund. Then spend more than
$100 and get yourself a better preamp.
>I noticed that the dbx mini-pre is using a Soviet made 12AX7 high-mu twin
>triode vacuum tube.
That is one of the best available.
>Should I replace this tube with a Genalex 12AX7 ($115) a Mullard 12AX7 ($60)
>or with a Telefuken 12AX7 tube? Will the noise go away?
No on all of those.
Jay Ts
Ted Roy
> this; chances that most of what you're hearing is thermal noise.
I have hiss similar what an audiocassette makes without any dolby noise
reduction at playback. The "shhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh" you know what
I mean.
> However, if it's mechanical noise that's being picked up by the tube
> (which you can easily gauge by gently tapping it) then trying different
> tubes might help.
Heeeey, I think you got a point here. I *ALSO* have mechanical noise. I
noticed that earlier today when I moved the unit to another place on my
desk, I heard these noises. It was like if the mini-pre had "an internal
microphone". Just to make sure that this mechanical sound isn't picked up by
my Shure SM-7, I unplugged the mic, left only the XLR cable and guess what:
Even the wire and the connector at the other end was acting like a
microphone! It was capturing the "sound of my touch".
HeHe......
I think that the dbx Mini-pre is a lemon, by design. (or all tube preamps
are like this). I don't know because this is my first experience with vacuum
tubes in general. And I'm in the process of discovering this "new world".
For me at least, tubes are new, even though they existed ages before
transistors.
Ted Roy
$115....
> for a 12AX7.....you....aren't being....serious, are you....nahh, couldn't
be...
Yap, check this web page out and see it yourself. A top-of-the-line 12AX7
costs $115:
http://www.audiotubes.com/12ax7.htm
Ted Roy
couldn't be...
.. oh forgot to mention that I saw another 12AX7 at $120 here:
http://www.thetubestore.com/12ax70ectyp.html
Ted Roy
>
> Isn't that more than the preamp itself costs?
Yap, it's double it's price actually. BUT, the tube that ships with the dbx
mini-pre costs $6.95 and I thought if I'll replace this cheap tube with a
better one, it will sound better. I think. The 12AX7 tubes are found here:
Ted Roy
> especially with soft sources.
I use my SM7 for vocals. More precisely for broadcast voice-overs. (Film /
TV / Radio).
Scott Dorsey
Ted Roy <ted...@hotmail.edu> wrote:
>I just purchased a brand new dbx mini-pre vacuum tube preamplifier. I tested
>it with a Shure SM-7 studio microphone just to find out that this pre-amp is
>noisy! I estimated the noise floor to be -50dB with both in/out gain set at
>75%. I unplugged the mic, just to hear if the mic/cable causes the noise:
>The noise was still present even without the mic/cable plugged at the input.
>
>The only way to make the noise dissapear is either lower the gain or shut
>down the unit.
>
>I noticed that the dbx mini-pre is using a Soviet made 12AX7 high-mu twin
>triode vacuum tube.
>
>Should I replace this tube with a Genalex 12AX7 ($115) a Mullard 12AX7 ($60)
>or with a Telefuken 12AX7 tube? Will the noise go away? Or it's simply the
>dbx mini-pre circuit that is noisy and not the soviet tube. I don't want to
>invest $115 in a premium quality "replacement" tube, just to find out that I
>just got 1 dB improvement in sound....
No. That tube doesn't really do anything much. The noise is mostly from
the solid-state front end. Dump it and get a preamp that sounds good.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Scott Dorsey
>But a S/N of 50 dB?
>
>SM7, DM57, whichever he uses, the S/N should be at least 90+ dB.
>
>I have measured 12AX7A's at -110dB.
Yes, but I bet they had more than 50V on the plate.
Scott Dorsey
>I think that the dbx Mini-pre is a lemon, by design. (or all tube preamps
>are like this). I don't know because this is my first experience with vacuum
>tubes in general. And I'm in the process of discovering this "new world".
>For me at least, tubes are new, even though they existed ages before
>transistors.
No, this is not a real tube preamp. For what it costs, you couldn't even
get an input transformer for a real tube preamp.
There are currently a LOT of people who have never heard real tube gear,
but who have bought into the hype about how they need tube equipment to
warm up their digital tracks, whatever that means. As a result, lots of
manufacturers are coming out with junk like this... a cheap solid state
preamp with a gimmick tube stuck in the middle of it. They don't sound
like real tube preamps and they don't work like them.
dbx is nowhere near the worst of the offenders either... I think ART
may have started the whole thing, although Aphex sure caught on fast....
now everybody and his brother is selling a fake tube preamp.
cram
> >it with a Shure SM-7 studio microphone just to find out that this pre-amp is
> >noisy!< <
Good advice from all. I would return the unit, something is wrong
with it. Even though it uses a starved plate design it shouldn't be
as noisy as you state. While changing the tubes does have a dramatic
sonic effect on starved plate designs, it does not make sense to spend
more for a tube than for the pre-amp. Additionally, $115 for a 12ax7
is outrageous, regardless of manufacture.
Tom Cram
dbx Senior Technical Support
(801) 568-7530
tc...@dbxpro.com
If we don't believe in freedom of expression for people we despise, we
don't believe in it at all.
-Noam Chomsky-
Monte P McGuire
Ted Roy <ted...@hotmail.edu> wrote:
>> If the noise is "hiss", it's unlikely that changing tubes will reduce
>> this; chances that most of what you're hearing is thermal noise.
Yeah, the front end uses 2N4403 transistors, and this won't get
changed with a tube swap. The tube is somewhere in the middle of the
preamp, and the front end stage, the solid state stage, is what
determines the input noise at high gains.
>Just to make sure that this mechanical sound isn't picked up by
>my Shure SM-7, I unplugged the mic, left only the XLR cable and guess what:
>Even the wire and the connector at the other end was acting like a
>microphone! It was capturing the "sound of my touch".
>HeHe......
Any preamp with a high input impedance will do this, and it's a
function of the cable itself, not the preamp. When you unplug the
mike, there is no load across pin 2 and 3 of the mike cable, so any
triboelectric noise from your mike cable will not be attenuated at
all. Put a 150 ohm resistor across pin 2 and 3 and repeat your
experiment. You will notice a lot less noise. Replace the cable with
a different model, perhaps one designed for low handling noise, and
the results will change still.
>I think that the dbx Mini-pre is a lemon, by design.
I personally see no reason to buy or use one... but for different
reasons.
>(or all tube preamps are like this). I don't know because this is my
>first experience with vacuum tubes in general.
This is very sad! There's a whole raft of useless, budget, bad
sounding gear out there and unfortunately, a lot of people spend a lot
of time trying to use this stuff. On the other hand, the market has
shown manufacturers that mosy hobbyist engineers won't generally pay
what it costs to manufacture quality gear, and that features, specs
and hype are worth more than something that simply sounds good, so I
guess this is what we end up with in the steady state.
Just say 'no' to this swill, use your ears before you buy, and over
time, perhaps this trend will reverse.
>For me at least, tubes are new, even though they existed ages before
>transistors.
A hint: you can have a really nice sounding preamp without any tubes.
Forget about the glowy thing and listen to the stuff before you buy
it. Does it sound exciting? Does it inspire you to play better or
sing more expressively? If not, pass on it. Also, get some
experience using good gear first before you buy the swill that's
available out there. Sure, some budget pieces are good, but that's
actually pretty rare. Most of the affordable stuff out there is
pretty painful to use.
OK, rant over...!
Take care,
Monte McGuire
mcg...@theworld.com
Dan Kennedy
>
> dbx is nowhere near the worst of the offenders either... I think ART
> may have started the whole thing, although Aphex sure caught on fast....
> now everybody and his brother is selling a fake tube preamp.
> --scott
>
Not everybody.
I know Mr. Hardy isn't. Nor Misters Hill, Fearn, Daking, Blackmer,
Massenburg, LaGrue, Upton, Tanner, Wolff, Farrant. And nothing
EveAnna makes is fake.
Dan Kennedy
Scott Dorsey
>
>> dbx is nowhere near the worst of the offenders either... I think ART
>> may have started the whole thing, although Aphex sure caught on fast....
>> now everybody and his brother is selling a fake tube preamp.
>
>I know Mr. Hardy isn't. Nor Misters Hill, Fearn, Daking, Blackmer,
>Massenburg, LaGrue, Upton, Tanner, Wolff, Farrant. And nothing
>EveAnna makes is fake.
Thank God!
Justin Ulysses Morse
<ted...@hotmail.edu> wrote:
If you have the money to buy exotic NOS preamp tubes, why not just buy
a preamp that doesn't suck? Me, I saved my credit cards and bought
some nice preamps. But I haven't shelled out big $$$ for expensive
preamp tubes, not even for my guitar amps. The sound difference I'm
able to perceive from one tube to the next is on par with turning the
volume or tone knobs tiny little increments. Mostly I would be unable
to pick the "good" tube by ear. So it seems really silly to fill my
$300 amplifier or $300 preamps with a bunch of $100 tubes.
And while I'm at it, let me just point out that you still have never
heard a tube preamp.
ulysses
geo...@gjhsun.cl.msu.edu
Mike Rivers
> Yap, check this web page out and see it yourself. A top-of-the-line 12AX7
> costs $115:
The concept of a "top-of-the-line" 12AX7 is something I find very
humorous. If I wanted something that sounded quieter than a 12AX7, I'd
get a solid state preamp. No toob sound here, none at all. Not that I
think it's bad, it's just too expensive these days if you don't want
it to sound like junk. On the other hand, some people like the sound
of tube junk because it sounds like junk. Others like the sound of
thousand-dollar tube gear because it sounds like real gear.
A $100 tube preamp? It'sa gimmick. If it does what you want, great. If
it doesn't, try something else. But it's worth trying another of the
same unit new from the store before you go swapping tubes. You DID buy
it from a dealer where you can check it out, didn't you? Or from a
dealer to whom you can return it, and have them check it out for you?
--
I'm really Mike Rivers (mri...@d-and-d.com)
Lynn Fuston
uly...@rollmusic.com wrote on 5/29/02 11:42 AM:
> If you have the money to buy exotic NOS preamp tubes, why not just buy
> a preamp that doesn't suck?
That would be WAY too easy. Think of the adventure, the spirit of trying out
new things, experimenting with technology. Putting $115 tubes into a $129
preamp is something that likely has never been done before.
Who knows? You just might end up with one very expensive, very average
preamp.
Live on the edge and experiment a little.
Peter Brown
> preamp.
This is the best answer I've read so far !!!!!! :-)
Tim
> Yap, check this web page out and see it yourself. A top-of-the-line 12AX7
> costs $115:
I bet you the price of that tube (not the tube itself, I meant the
ka-ching) that if I sent you 5 "specially selected" tubes from my
collection, they would sound as good, or better. And it would be
cheaper too.
Mikkel C. Simonsen
>
> Should I replace this tube with a Genalex 12AX7 ($115) a Mullard 12AX7 ($60)
> or with a Telefuken 12AX7 tube? Will the noise go away? Or it's simply the
> dbx mini-pre circuit that is noisy and not the soviet tube. I don't want to
> invest $115 in a premium quality "replacement" tube, just to find out that I
> just got 1 dB improvement in sound....
Paying even $60 for a 12AX7 tube is madness... The "soviets", slovakians
and serbians actually make very good tubes. Tesla/JJ makes a good
ECC803S for instance (on old Telefunken equipment) - and it might be a
bit cheaper than a Telefunken.
If you want to try the "exotic" 12AX7s find a used tube in some
equipment. Those tubes work very well even if they have been used for 15
years.
Best regards,
Mikkel C. Simonsen
ThreeMile
Hmmm, I believe Daking, Blackmer (R.I.P.), and Massenburg are all solid-state
designs.
Mike Rippe
Ted Roy
Ok Ok Ok. Now guys don't flame me... I think that the error comes from my
side. I plugged the mic to the dbx mini-pre using the unbalanced 1/4" TS
connector. I used a 15ft XLR to 1/4" unbalanced cable.... The noise level
is unnaceptable. I'm talking abour "real hiss" here.
Then, today I tried testing this unit with a XLR to XLR, and guess what. The
noise floor from -50dB went "CONSIDERABLY* down.
Conclusion. Don't use the dbx mini-pre unbalanced inputs, because it's
noisy. With its XLR in/outs it's a pretty good pre-amp, considering the junk
tube that's included inside. The Sovtek 12AX7WA that ships with the preamp,
is the cheapest of the cheapiest tubes available on earth.. I did sonme
research and I rad that the 12AX7WA is a "bad thing to have".
Oh, one more thing, I will also replace the tube with a Ei 12AX7 or Sovtek
12AX7LPS. Is will inmprove noise floor.
I'll use the preamp with a Shure SM-7 and with a Marshall MXL 2003 mics for
voice-overs.
So, among these two tubes, (Ei 12AX7 Vs. Sovtek 12AX7WA) which one will be
the best for vocals?
Lynn Fuston
ted...@hotmail.edu wrote on 5/29/02 6:39 PM:
> So, among these two tubes, (Ei 12AX7 Vs. Sovtek 12AX7WA) which one will be
> the best for vocals?
Plug them in and decide for yourself.
Gregg
Just kidding ;-)
Glad you solved the problem :-D
However 2N4403's are crappy for front end. If you are handy at
re-engineering low-end things, you might wanna drop in 2N5087's and
re-bias their stage. You could use a lower Icc and get a minimum 20 dB
better NF.
You CAN use the unbalanced inputs, just use an inline transformer.
That trick works well in studio, so why not for you?
As for best types of 12AX7's, if you have more than 10% NFB, it won't
matter a lot, especially with a starved plate. If there is no NFB,
really a 12AX7 is the wrong tube to run at low Va, IMO.
--
Gregg
On Wed, 29 May 2002 19:39:59 -0400, "Ted Roy" <ted...@hotmail.edu>
wrote:
Jeff Thompson
"Mikkel C. Simonsen" <m...@post5.tele.dk> wrote in message
news:3CF568...@post5.tele.dk...
> Ted Roy wrote:
> >
> > Should I replace this tube with a Genalex 12AX7 ($115) a Mullard 12AX7
($60)
> > or with a Telefuken 12AX7 tube? Will the noise go away? Or it's simply
the
> > dbx mini-pre circuit that is noisy and not the soviet tube. I don't want
to
> > invest $115 in a premium quality "replacement" tube, just to find out
that I
> > just got 1 dB improvement in sound....
>
> Paying even $60 for a 12AX7 tube is madness... The "soviets", slovakians
> and serbians actually make very good tubes. Tesla/JJ makes a good
> ECC803S for instance (on old Telefunken equipment) - and it might be a
> bit cheaper than a Telefunken.
>
> If you want to try the "exotic" 12AX7s find a used tube in some
> equipment. Those tubes work very well even if they have been used for 15
> years.
>
> Best regards,
>
> Mikkel C. Simonsen
reasonable prices is http://pages.prodigy.net/jimmcshane/ No connection -
just a satisfied customer.
Jeff Thompson
Shiva
> > If the noise is "hiss", it's unlikely that changing tubes will reduce
> > this; chances that most of what you're hearing is thermal noise.
>
> I have hiss similar what an audiocassette makes without any dolby noise
> reduction at playback. The "shhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh" you know
what
> I mean.
>
That's the noise... Low-qualit resistors (and underrated resistors), thin
runners on PC boards, low quality pots - it al adds up...
> > However, if it's mechanical noise that's being picked up by the tube
> > (which you can easily gauge by gently tapping it) then trying different
> > tubes might help.
>
> Heeeey, I think you got a point here. I *ALSO* have mechanical noise. I
> noticed that earlier today when I moved the unit to another place on my
> desk, I heard these noises. It was like if the mini-pre had "an internal
> microphone". Just to make sure that this mechanical sound isn't picked up
by
> my Shure SM-7, I unplugged the mic, left only the XLR cable and guess
what:
> Even the wire and the connector at the other end was acting like a
> microphone! It was capturing the "sound of my touch".
> HeHe......
>
well, there are *good cables* & there are *cheap cables.* Even with
balanced cables, you'll hear them when you whip them against the floor -
that's usually the cable, not the preamp (though I don't doubt that the
preamp's a dud).
Finally, *all* tubes are microphonic to some extent, and, in high-gain
circuits, this microphonics are pretty notisable. So try not to drop the
thing too often, or keep it on top of a stack, or on a comouter desk 9unless
you want to record your HD spinnin' up) or next to anything like a computer
monitor (all kinds of nasty noise) or a computer (same dealey).
> I think that the dbx Mini-pre is a lemon, by design. (or all tube preamps
> are like this).
No, not all, but the good ones are prycy enough to make you want to stop
singing...
> I don't know because this is my first experience with vacuum
> tubes in general. And I'm in the process of discovering this "new world".
> For me at least, tubes are new, even though they existed ages before
> transistors.
Have fun, and think "58!!!"
Dan Kennedy
Bullshit.
3? maybe.
That's almost as stupid as saying a BC284 is lightyears better
than an MPS-A18.
You been buying $125 12AX7's too?
Dan Kennedy
Great River Electronics Inc.
Monte P McGuire
>20db from 4403's to 5087's?
>
>Bullshit.
Yeah, and not from a lower Icc either. Most transistors are quieter
with low Z loads when you crank up the bias current. 1mA seems to be
about right most of the time.
Regards,
Monte McGuire
mcg...@theworld.com
Jay Ts
>
> ted...@hotmail.edu writes:
>> A top-of-the-line 12AX7 costs $115:
>
>The concept of a "top-of-the-line" 12AX7 is something I find very
>humorous. If I wanted something that sounded quieter than a 12AX7, I'd
>get a solid state preamp.
That's what I decided too, so I got a M Audio DMP3. It's not by
any means (!) the greatest mic pre, but it's _worlds_ better than
the Presonus Blue Tube (starved plate design) that I tried out
and quickly returned. And only $200 for 2 channels.
The DMP3 will do ok for me at least until the RNMP is available,
or I save up for a Grace Model 101 or Millenia or something of
that order.
Jay Ts
Jay Ts
>
>Paying even $60 for a 12AX7 tube is madness... The "soviets", slovakians
>and serbians actually make very good tubes. Tesla/JJ makes a good
>ECC803S for instance (on old Telefunken equipment) - and it might be a
>bit cheaper than a Telefunken.
There's also the Yugo EI ECC83/12ax7. The Ei factory used to be
one of Telefunken's contractors, and word is that they are still
making the 12ax7's pretty much the same. You can get them brand
new for just $8, so why bother with NOS Tele's (which might better
be classified as "used" in some cases than NOS ;-) ... just to have
the double diamond on the bottom? :)
I've been using Ei 12ax7s here, and I love them. I prefer them
to Teslas, Sovteks, and a few other oddball 12ax7s that I've
tried. I hear a big difference, and the Ei 12ax7s sound much
more musical to my ears.
Jay Ts
Jay Ts
to rec.audio.TUBES until I got here and read it! I did
not mean to promote solid state preamps in a tubes newsgroup.
If I had Real Money, I'd buy from Manley Labs. Am I forgiven? :)
Jay Ts
Gregg
I have designed low noise circuits for 25 years. And your credentials
are????????
I happen to have used 4403's and 5087 extensively and know quite well
what I speak of.
Great River Electronics? River of what?
--
Gregg
On Thu, 30 May 2002 02:32:48 GMT, Dan Kennedy <Dken...@minn.net>
wrote:
Greg Pierce
Regardless of the noise source, I think we can agree on some basic things:
1 - At a $129.99 price point, a quiet mike preamp would probably use good
quality op-amps - end of story. It probably wouldn't sound too bad,
either
(though not as good as the better discrete transistor or tube designs).
2 - Sorry if I offend anyone here, but... the 12AX7 sucks as a high-gain
stage for
low-level signals. Better to use a high-gm triode or a pentode (the
EF86 is amazingly
quiet despite its relatively low gm). Also, the plate voltage should
be run at or near its
maximum rating, and the tube biased accordingly - this is my opinion
based on my
experience; many will disagree and give good reasons why this isn't
the best way to
operate a low level tube stage. They may be right, but I stick to my
opinion on this one.
And yes, I know pentodes are supposed to be noisier than triodes due
to partition noise;
however, the high gain of the pentode stage can (and does) often
shift the S/N ratio in
its favor. Anyway, if I were to use a high-mu, low gm triode, I
would take a 6SL7 over
any 12AX7 any day...
3 - If you truly want the highest S/N, and money is no object, use a
high quality, well shielded
transformer and feed it into an equally superb quality preamp. The
right transformer will drastically
reduce the burden on the preamp (ask anyone with a super low output
moving coil phono cartridge),
but the wrong transformer will be really horrible.
4 - Many of these 'starved plate' preamps are simply designed as an
'effect', not a preamp. The 'engineers'
who create these things think that the 'tube sound' is distortion,
so why not starve the plate and get some
REALLY good distortion! That is their theory anyway. Thats about as
logical as building a 'starved transistor'
stage to get that 'transistor sound'...
Anyway, my vote is this; if you are short on cash and need a decent mike
pre, spend the money on a decent solid-
state unit from a reputable manufacturer, rather than some cheap
wanna-be tube 'preamp'. On the other hand, if
you have plenty of green and want the truly best sound quality and the
highest dynamic range, you cant beat a good,
WELL ENGINEERED tube design.
Just my $0.02 - and then some :-p
Greg
Ted Roy wrote:
>I just purchased a brand new dbx mini-pre vacuum tube preamplifier. I tested
>it with a Shure SM-7 studio microphone just to find out that this pre-amp is
>noisy! I estimated the noise floor to be -50dB with both in/out gain set at
>75%. I unplugged the mic, just to hear if the mic/cable causes the noise:
>The noise was still present even without the mic/cable plugged at the input.
>
>The only way to make the noise dissapear is either lower the gain or shut
>down the unit.
>
>I noticed that the dbx mini-pre is using a Soviet made 12AX7 high-mu twin
>triode vacuum tube.
>
>Should I replace this tube with a Genalex 12AX7 ($115) a Mullard 12AX7 ($60)
>or with a Telefuken 12AX7 tube? Will the noise go away? Or it's simply the
>dbx mini-pre circuit that is noisy and not the soviet tube. I don't want to
>invest $115 in a premium quality "replacement" tube, just to find out that I
>just got 1 dB improvement in sound....
>
Ted Roy
> as noisy as you state.
Tom, as I stated on one of my latest messages, my configuarion was such that
caused the mini-pre to get noisy.
If you want to reproduce this noise which I experienced, you'll need the
following:
Shure SM-7 mic
15ft XLR to 1/4" TS Unbalanced microphone cable
6ft 1/4" TS unbalanced to RCA cable
Plug the XLR connector to the microphone, then plug the other end (1/4"
Unbalanced) to the mini-pre.
Plug the 1/4" to the output into the power amplifier and you will get the
noise wich I initially described.
Go all the way XLR Balanced and all the noises dissapear! To my
understanding, the mini-pre doesn't like unbalanced inputs.
Although you have to admit that you're not using a good tube, such as the
one that you currently ship it with (Sovtek 12AX7WA) considering $3 more and
you could ship it with a lot better one such as the Sovtek 12AX7LP or Ei
12AX7.
Keep up the good work, you make good products. AND, I really appreciate that
somebody from dbx actually looks at the newsgroups, reads user feedback and
takes the time to answer a thead on one of their products. This actually
contributes a lot towards quality control.
Having said this, just consider including a better tube, and you may also
want to investigate why the mini-pre causes a lot of noise when an mic is
plugged in the unbalanced input without a tranformer.
I the past, I plugged many times the same mic directly to the unbalanced
input, using the same cable to the front 1/4" inputs of Broadcast VCRs. I
never had noise problems. So I must conclude that the mini-pre gets quiet
with XLR and gets mad with 1/4"... Nevertheless, after I discovered that I
should use XLR-XLR with the mini-pre, I found the unit to be exacly what I
was looking for. I ordered a replacement Ei 12AX7 tube and I can't wait till
I'll get it and put it in. I'll transform the dbx mini-pre into a "dbx
mini-pre PRO MKII"
again,
I really appreciate your feedback, and we all do.
Preben Friis
"Gregg" <nos...@unknown.com> wrote in message
news:3cf5d3d6...@news.telus.net...
> And we are to accept the advice of a foul mouthed opinion like you?
>
> I have designed low noise circuits for 25 years. And your credentials
> are????????
>
> I happen to have used 4403's and 5087 extensively and know quite well
> what I speak of.
>
> Great River Electronics? River of what?
>
> --
> Gregg
Watch your shoes... You just stepped in someting that smells bad...
Check these:
http://www.greatriverelectronics.com
http://groups.google.com/groups?hl=en&lr=&q=Great+River+group%3Arec.audio.pr
o
/Preben Friis
Dan Kennedy
> And we are to accept the advice of a foul mouthed opinion like you?
>
> I have designed low noise circuits for 25 years. And your credentials
> are????????
>
> I happen to have used 4403's and 5087 extensively and know quite well
> what I speak of.
>
> Great River Electronics? River of what?
>
> --
> Gregg
From my trusty 1987 Motorola Small signal book:
NF: 2N4403 from .2 to 100 Khz, 1ma collector current for optimum
source impedance of 430 ohms, less than 1db.
We are talking mic inputs here, so 430 as source may be a bit high but
it's ok.
While the data is presented a bit differently for the 5087 it actually
is shown as being on the 3db countour line for a 4-500 ohm source.
20db? really.
Bullshit.
I've been doing it for a bit too. My name and credentials are in my post.
You are?
Choky
GOT forgives you.......
--
Choky
Prodanovic Aleksandar
choky*remove*@eunet.yu
YU
-------------------------------
remove *remove* to reply!
-------------------------------
"Jay Ts" <jay...@sedonaDOT.net> wrote in message
news:slrnafbfvo....@toltec.metran.cx...
cram
> one that you currently ship it with (Sovtek 12AX7WA) considering $3 more and
> you could ship it with a lot better one such as the Sovtek 12AX7LP or Ei
> 12AX7.<
I will admit that readily. We move a lot of product and we need an
inexpensive steady supply of tubes that is not subject to price or
availablility fluctuations. At least that is what the guys upstairs
tell me :).
> Keep up the good work, you make good products. AND, I really appreciate that
> somebody from dbx actually looks at the newsgroups, reads user feedback and
> takes the time to answer a thead on one of their products. This actually
> contributes a lot towards quality control.
Thanks man. That is actually why I'm here, for tech support. The
occassional flame war that I'll participate in is for personal
amusement only:D.
> Having said this, just consider including a better tube, and you may also
> want to investigate why the mini-pre causes a lot of noise when an mic is
> plugged in the unbalanced input without a tranformer.
I will pass that on to the guys that can do something about it.
> I really appreciate your feedback, and we all do.
You can also e-mail or call me directly for info if you need it. I'm
here 8-5 (MST) M-F. Make good music.
Tom Cram
dbx Senior Technical Support
(801) 568-7530
tc...@dbxpro.com
If we don't believe in freedom of expression for people we despise, we
don't believe in it at all.
-Noam Chomsky-
Scott Dorsey
>And we are to accept the advice of a foul mouthed opinion like you?
>
>I have designed low noise circuits for 25 years. And your credentials
>are????????
Well, Dan makes one of the best preamps I ever used.
>I happen to have used 4403's and 5087 extensively and know quite well
>what I speak of.
>
>Great River Electronics? River of what?
You can gain an awful lot going from a 2N4403 to a 2N5087, although you
gain a lot more consistency than improved noise figure in most cases.
Depends a lot on where that 2N4403 came from, since it's basically a pretty
open spec. But I have heard some pretty surprisingly low noise stuff done
with the 2N4403 (the Mackie input stage being a great example).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Scott Dorsey
>2 - Sorry if I offend anyone here, but... the 12AX7 sucks as a high-gain
>stage for
> low-level signals. Better to use a high-gm triode or a pentode (the
>EF86 is amazingly
> quiet despite its relatively low gm).
Don't forget frame grid tubes either!
So, what is the story on the EF86 now? I am seeing EF86 prices going way
up and have heard some rumour that Svetlana isn't making the things any more.
I really liked the EF86 and of course it's about the only current production
low noise pentode.
> Anyway, if I were to use a high-mu, low gm triode, I
>would take a 6SL7 over
> any 12AX7 any day...
Depends. I really like the Russian 6SL7 and 6SN7, but they have a lot of
filament/cathode leakage so you gotta run them on DC and the two halves
are never quite identical. I get better consistency with the JJ 12AX7.
>3 - If you truly want the highest S/N, and money is no object, use a
>high quality, well shielded
> transformer and feed it into an equally superb quality preamp. The
>right transformer will drastically
> reduce the burden on the preamp (ask anyone with a super low output
>moving coil phono cartridge),
> but the wrong transformer will be really horrible.
I thought we were talking about mike preamps, which pretty much all include
an input transformer (unless they are using a solid state impedance converter
before the tube, and most of the stuff doing that is worthless junk).
>4 - Many of these 'starved plate' preamps are simply designed as an
>'effect', not a preamp. The 'engineers'
> who create these things think that the 'tube sound' is distortion,
>so why not starve the plate and get some
> REALLY good distortion! That is their theory anyway. Thats about as
>logical as building a 'starved transistor'
> stage to get that 'transistor sound'...
Where do these people come from anyway?
And hey, I have heard a particular parametric equalizer built with amp
modules that use input transistors with a 1M source resistor for low noise.
Wanna talk about weird starved transistor sound, it's got plenty.
Chris Coleman
> "Gregg" <nos...@unknown.com> wrote in message
> news:3cf5d3d6...@news.telus.net...
> > And we are to accept the advice of a foul mouthed opinion like you?
> >
> > I have designed low noise circuits for 25 years. And your credentials
> > are????????
> >
> > I happen to have used 4403's and 5087 extensively and know quite well
> > what I speak of.
> >
> > Great River Electronics? River of what?
> >
> > --
> > Gregg
>
> Watch your shoes... You just stepped in someting that smells bad...
Hilarious...this should be fun to watch.
Gregg
source at 4-500 uA Icc. Vcc was 11 volts, biased at V+/2.
Compared to a 2N4403 in equivalent circuit.
The NF was 20 dB difference measured, repeated threee times by 2
different people.
My Credentials are:
Co-founder - Antares Antenna Systems, HF and VHF-Lo band antennas.
Owner - Hatzic Electronic Repair, later to focus on analog audio
engineering than consumer repair.
Owner/Operator - Small Business Services, Web design and maintenence.
Nice chatting with you once calm, sir.
(thread *plonked*)
--
Gregg
On Thu, 30 May 2002 13:22:51 GMT, Dan Kennedy <dken...@minn.net>
wrote:
Greg Pierce
Ahh yes... Open mouth - insert foot :-p
Greg
Greg Pierce
>Greg Pierce <greg....@cox.net> wrote:
>
>>2 - Sorry if I offend anyone here, but... the 12AX7 sucks as a high-gain
>>stage for
>> low-level signals. Better to use a high-gm triode or a pentode (the
>>EF86 is amazingly
>> quiet despite its relatively low gm).
>>
>
>Don't forget frame grid tubes either!
>
>So, what is the story on the EF86 now? I am seeing EF86 prices going way
>up and have heard some rumour that Svetlana isn't making the things any more.
>I really liked the EF86 and of course it's about the only current production
>low noise pentode.
>
Yup, out of production as far as I know. Speaking of frame-grid tubes,
what is that one
frame-grid high-gm pentode that Eric Barbour talked about in a past
issue of VTV? If
I remember correctly, it was supposed to be very quiet and very linear
(and very out of
production).
>
>> Anyway, if I were to use a high-mu, low gm triode, I
>>would take a 6SL7 over
>> any 12AX7 any day...
>>
>
>Depends. I really like the Russian 6SL7 and 6SN7, but they have a lot of
>filament/cathode leakage so you gotta run them on DC and the two halves
>are never quite identical. I get better consistency with the JJ 12AX7.
>
However, if you dont mind using NOS.....
>
>>3 - If you truly want the highest S/N, and money is no object, use a
>>high quality, well shielded
>> transformer and feed it into an equally superb quality preamp. The
>>right transformer will drastically
>> reduce the burden on the preamp (ask anyone with a super low output
>>moving coil phono cartridge),
>> but the wrong transformer will be really horrible.
>>
>
>I thought we were talking about mike preamps, which pretty much all include
>an input transformer (unless they are using a solid state impedance converter
>before the tube, and most of the stuff doing that is worthless junk).
>
I was under the impression that the dbx pre didn't use an input
tranny... if it does, is it a
good quality unit with the proper impedance match?
>>4 - Many of these 'starved plate' preamps are simply designed as an
>>'effect', not a preamp. The 'engineers'
>> who create these things think that the 'tube sound' is distortion,
>>so why not starve the plate and get some
>> REALLY good distortion! That is their theory anyway. Thats about as
>>logical as building a 'starved transistor'
>> stage to get that 'transistor sound'...
>>
>
>Where do these people come from anyway?
>
Well rounded graduates of liberal arts colleges - modern rennaissance
men if you ask em...
>
>And hey, I have heard a particular parametric equalizer built with amp
>modules that use input transistors with a 1M source resistor for low noise.
>Wanna talk about weird starved transistor sound, it's got plenty.
>--scott
>
Greg
Scott Dorsey
>
>Yup, out of production as far as I know. Speaking of frame-grid tubes,
>what is that one
>frame-grid high-gm pentode that Eric Barbour talked about in a past
>issue of VTV? If
>I remember correctly, it was supposed to be very quiet and very linear
>(and very out of
>production).
I dunno. But then, I always like the 12BY7 and the 6AU6. So, are there
ANY small signal pentodes in the current catalogues?
>>I thought we were talking about mike preamps, which pretty much all include
>>an input transformer (unless they are using a solid state impedance converter
>>before the tube, and most of the stuff doing that is worthless junk).
>>
>I was under the impression that the dbx pre didn't use an input
>tranny... if it does, is it a
>good quality unit with the proper impedance match?
No, the dbx uses a solid state impedance converter in front and it's in
the category I would tend to consider worthless junk.
Janice....@macca5.fsnet.co.uk
"Greg Pierce" <greg....@cox.net> wrote in message
news:3CF5E612...@cox.net...
> Well, I suppose I should chime in here...
Why !!
> Regardless of the noise source, I think we can agree on some basic things:
>
> 1 - At a $129.99 price point, a quiet mike preamp would probably use good
> quality op-amps - end of story. It probably wouldn't sound too bad,
> either
Very true, but for Christ's sake don't tell anybody. This is a tube group
!!.
Also keep it to yourself that it would probably cost less than $5, never
mind $129.99.
> (though not as good as the better discrete transistor or tube
designs).
OK I'll go to $10
> 2 - Sorry if I offend anyone here, but... the 12AX7 sucks as a high-gain
> stage for
> low-level signals. Better to use a high-gm triode
Sorry, thought the 12AX7/ECC83 was a high gm triode ? Is there a higher gm
one out there I haven't spotted yet ? and with the right loads it's actually
not too bad. Pity it just looks such a little shit.
or a pentode (the
> EF86 is amazingly
> quiet despite its relatively low gm).
Also, the plate voltage should
> be run at or near its
> maximum rating, and the tube biased accordingly - this is my opinion
> based on my
> experience; many will disagree and give good reasons why this isn't
> the best way to
> operate a low level tube stage. They may be right, but I stick to my
> opinion on this one.
Each to his own my son. Who am I to argue, but they sound like somebody
frying a steak to me. Break
in the music ? You can always listen to the EF86 I suppose
> And yes, I know pentodes are supposed to be noisier than triodes due
> to partition noise;
> however, the high gain of the pentode stage can (and does) often
> shift the S/N ratio in
> its favor.
If you could shift the noise out to somewhere the other side of 50kHz, I
could go for it.
Anyway, if I were to use a high-mu, low gm triode, I
> would take a 6SL7 over
> any 12AX7 any day...
Now, hey man, hit me with some more of these positive waves !!!!!!!!
6SL7/6SN7 --- proper big boys valves--------the real thing !!!!!! The dog's
bollocks !!!!!!! ECC what
???
Give 'em to the girls to play with !!!! Grab a beer and let's go.
> 3 - If you truly want the highest S/N, and money is no object, use a
> high quality, well shielded
> transformer and feed it into an equally superb quality preamp. The
> right transformer will drastically
> reduce the burden on the preamp (ask anyone with a super low output
> moving coil phono cartridge),
> but the wrong transformer will be really horrible.
Or just buy the $5 SS preamp
> 4 - Many of these 'starved plate' preamps are simply designed as an
> 'effect', not a preamp. The 'engineers'
> who create these things think that the 'tube sound' is distortion,
> so why not starve the plate and get some
> REALLY good distortion! That is their theory anyway. Thats about as
> logical as building a 'starved transistor'
> stage to get that 'transistor sound'...
Just at the minute working on a 2 x 6SL7 preamp which is an input and output
RCA socket which are joined internally for -- wait for it !! Unity gain.
!!
Sounds good hey !! No losses at all. No distortion and no noise either !!
Makes you want it already doesn't it ??
A 6 v transformer keeps the valves warm and in a hand crafted rosewood case
I reckon I can get it away at about $1500
> Anyway, my vote is this; if you are short on cash and need a decent mike
> pre, spend the money on a decent solid-
> state unit from a reputable manufacturer, rather than some cheap
> wanna-be tube 'preamp'. On the other hand, if
> you have plenty of green and want the truly best sound quality and the
> highest dynamic range, you cant beat a good,
> WELL ENGINEERED tube design.
With you all the way.(apart from the EF86s) and particularly the WELL
ENGINEERED bit. (and the 6SL7s of course)
Regards
jimmy
Choky
hehe,I already know that EI 12AX7 is good ............
--
Choky
Prodanovic Aleksandar
choky*remove*@eunet.yu
YU
-------------------------------
remove *remove* to reply!
-------------------------------
"Ted Roy" <ted...@hotmail.edu> wrote in message
news:wFdJ8.43460$l25.2...@weber.videotron.net...
Peter Brown
You may also want to suggest what Greg Piece wrote further down in the
messages. It's worth it. The mini-pre might cost a bit more, but if it
sells, I think it's a deal for dbx.
jim andrews
> My Credentials are:
>
> Co-founder - Antares Antenna Systems, HF and VHF-Lo band antennas.
> Owner - Hatzic Electronic Repair, later to focus on analog audio
> engineering than consumer repair.
> Owner/Operator - Small Business Services, Web design and maintenence.
>
> Nice chatting with you once calm, sir.
>
> (thread *plonked*)
Gregg,
Why *plonk* the thread? Dan Kennedy knows his stuff, and the
proof is in the pudding. His preamps are incredible. Now, I
don't *know* if you know your stuff, but it seems as if you
might (and it's simple courtesy to assume you do until you
prove otherwise), so why not hang around and let's sort this
out?
Me, I wouldn't know a transistor from a transvestite, but I
think r.a.pro could stand a whole lot more of this kind of nuts
and bolts talk. In my experience, when two people disagree so
vehemently about something they're both knowledgable about, it
usually comes down to some sort of miscommunication. One guy
is talking about apples, the other guy is talking about pears.
Hang tight and clear this up with Dan, why don't you? He's
one of the tame ones around here. He doesn't bite.
jim andrews
basset sound
austin, tx
hank alrich
> > "Gregg" <nos...@unknown.com> wrote in message
> > news:3cf5d3d6...@news.telus.net...
> > > Great River Electronics? River of what?
Quality. Seriously good quality. Check it out.
--
hank alrich * secret__mountain
audio recording * music production * sound reinforcement
"If laughter is the best medicine let's take a double dose"
Dan Kennedy
for a source impedance 50 to 100 times that of the actual requirements
"proves" the better noise performance of one transistor over another?
Repeat the performance with real world source impedances and dynamic
range requirements and the differences will largely disappear.
Seems to me to get 20db difference you had something parasitic going
on.
Mikkel C. Simonsen
>
> Yup, out of production as far as I know. Speaking of frame-grid tubes,
> what is that one
> frame-grid high-gm pentode that Eric Barbour talked about in a past
> issue of VTV? If
> I remember correctly, it was supposed to be very quiet and very linear
> (and very out of
> production).
E180F/6688. I bought a couple from AES when they were on sale, but I
haven't done anything with them yet...
Best regards,
Mikkel C. Simonsen
Tim
> > (thread *plonked*)
>
> Gregg,
>
> Why *plonk* the thread?
Always kinda funny how one guy plonks someone or something, then someone
adds to that...surely he knows that the guy won't be reading it...
Tim
--
"WOOHOO! Who would've guessed reading and writing would pay off!"
- Homer Simpson
Greg Pierce
>"Greg Pierce" <greg....@cox.net> wrote in message
>news:3CF5E612...@cox.net...
>
>>Well, I suppose I should chime in here...
>>
>
>Why !!
>
Because I can.
>
>>Regardless of the noise source, I think we can agree on some basic things:
>>
>>1 - At a $129.99 price point, a quiet mike preamp would probably use good
>> quality op-amps - end of story. It probably wouldn't sound too bad,
>>either
>>
>
>Very true, but for Christ's sake don't tell anybody. This is a tube group
>!!.
>Also keep it to yourself that it would probably cost less than $5, never
>mind $129.99.
>
>> (though not as good as the better discrete transistor or tube
>>
>designs).
>
>OK I'll go to $10
>
>>2 - Sorry if I offend anyone here, but... the 12AX7 sucks as a high-gain
>>stage for
>> low-level signals. Better to use a high-gm triode
>>
>
>Sorry, thought the 12AX7/ECC83 was a high gm triode ? Is there a higher gm
>one out there I haven't spotted yet ? and with the right loads it's actually
>not too bad. Pity it just looks such a little shit.
>
No, the 12AX7 is a high-mu triode, not high-gm - two different things
The EF86 is a sleeper - connect the screen and suppressor to the plate
and you have a damn
good triode.
Greg
Gregg
Had I looked in my Newsgroups bar and noticed thre cross-post, I
wouldn't have even responded.
Jim seems nice, maybe the other guy is too, but I can't stand foul
lingo.
If it was civil toungued, I wouldn't have felt the need to plonk. I
don't mind debate and I will admit it when I am wrong, but be darned
if I will have somone, smart or ID-10-T, start swearing at me for
sharing findings or offering advice. I gotsa plenty o' http forms to
do battle on for that (being a mod can suck!) ;-)
I think I'll just stay home with my R.A.T. buddies where it's quiet
:-D
--
Gregg
On Thu, 30 May 2002 19:25:25 -0500, "Tim" <tmor...@charter.net>
wrote:
Monte P McGuire
Greg Pierce <greg....@cox.net> wrote:
>2 - Sorry if I offend anyone here, but... the 12AX7 sucks as a high-gain
>stage for low-level signals.
...which isn't happening inside of the dbx mini pre. The tube is
somewhere after the first gain stage, so it's noise contribution
should be pretty negligible, at least at significant gains.
>Anyway, if I were to use a high-mu, low gm triode, I would take a
>6SL7 over any 12AX7 any day...
Use the right input transformer, and either could work pretty well
noise wise. Stick the tube after a solid state front end and you
realize that the tube's noise contribution isn't the most critical one
in the preamp.
>3 - If you truly want the highest S/N, and money is no object, use a
>high quality, well shielded transformer and feed it into an equally
>superb quality preamp.
This is now a 'real' tube preamp is designed. Peavey seems to manage
this with a pretty low street price - the VMP-2 uses a transformer in
and out and it's all tube. (BTW, it uses a 12AX7 for the low level
stages and not only is is quiet, but it sounds pretty darn good too.
I 'blueprinted' one recently, replacing all the stock resistors and
capacitors with better quality ones and it honestly sounds pretty
amazing.)
For the lowest noise though, I wouldn't use a transformer (and
therfore a tube) at all, simply because of the dB or two of insertion
loss from the transformer. A transformerless design like Dan
Kennedy's that uses low noise JFETs for the front end would probably
be quietest among all possible topologies.
Heck, if money is no object, why not consider cryogenic cooling as
well ;-) There's no reason why you can't change the 'T' in En =
sqrt(4KTRb)
>Anyway, my vote is this; if you are short on cash and need a decent mike
>pre, spend the money on a decent solid-
>state unit from a reputable manufacturer, rather than some cheap
>wanna-be tube 'preamp'. On the other hand, if
>you have plenty of green and want the truly best sound quality and the
>highest dynamic range, you cant beat a good,
>WELL ENGINEERED tube design.
If you're short on cash, my suggestion is to save your money and find
a different hobby! Nobody _needs_ to record, and some of this gear is
doomed to be come landfill. Why spend good money on something that
will waste your time, squander your opportunities and have to be
replaced sometime in the future?
Buying time in a real studio would be infinitely more productive,
IMHO.
Regards,
Monte McGuire
mcg...@theworld.com